1. Field of the Invention
The present invention relates to a channel prediction device in an OFDM (Orthogonal Frequency Divisional Multiplexing)-CDMA (Code Divisional Multiple Access) system and a method thereof.
2. Description of the Related Art
Recent advancements in communication technologies have been remarkable and systems communicating large amounts of data at high speed have been realized. This phenomenon not only applies to wired communication, but also wireless communication. Specifically, with the spread of mobile terminals, such as, cellular phones and the like, research and development has created wireless systems where a large amount of data can be communicated at high speed, and multimedia data, such as dynamic images, voice and the like, can be handled by mobile terminals.
Recently, high-speed wireless communication based on CDMA called “the third generation” has been developed and is about to be put into practical use. In response to this trend, wireless communication R&D departments have started to research and develop the fourth generation wireless communication system aiming at larger-capacity and higher-speed wireless communication.
OFDM-CDMA is a strong candidate for the basic system of the fourth generation mobile communication system. In this system, an OFDM technology for transmitting a plurality of pieces of data in parallel using a plurality of sub-carriers each with a mutually orthogonal frequency and a CDMA technology using the orthogonality of a spread code by which user data is multiplied when a plurality of pieces of user data are multiplexed, are united in order to realize larger-capacity, higher-quality and higher-speed communication.
However, currently the OFDM-CDMA system is still in a proposal stage and in an R&D evaluation stage, and individual technologies required for an actual system must be developed.
In particular, channel prediction conducted in the third generation W-CDMA system and the like must also be conducted in an OFDM-CDMA system. In this case, the channel prediction value is indispensable for restoring amplitude modulation or phase rotation that signals undergo in order to propagate in the air, to normal and for detecting correct signals. However, when the channel prediction value is calculated in a W-CDMA system, usually a channel prediction value averaged in a time direction is used.
Since signals are affected by noise when propagate in the air, the influence of noise must be eliminated. Therefore, in order to obtain a correct channel prediction value in a W-CDMA system, channel prediction values calculated using a plurality of pilot signals are averaged in a time direction.
However, in an OFDM-CDMA system, in order to obtain a more accurate channel prediction value, channel prediction values are averaged not only in a time direction but also in a sub-carrier direction, since a plurality of sub-carriers are used.
However, the detailed contents of a method for calculating a channel prediction value in an OFDM-CDMA system are not still unclear.